In the sampling of fluid contaminants, numerous techniques are known. Of those used in the sampling of lethal and non-lethal contaminants, that disclosed and patented by Robertson in U.S. Pat. No. 3,628,915, has shown much promise and has been used by the common assignee. So also, his portable sampler has met with success, both under controlled and field conditions, and is presently being used.
The Robertson disclosed sampling apparatus and process, herein incorporated by references, is explained below. The apparatus comprises opposing hinged and apertured blocks between which is temporarily sandwiched filter collecting medium. One of the above mentioned apertures is closed by a suction pump hose. The other block aperture remains open for the atmosphere or sample medium. In operation, a differential pressure is created at the filter by actuating the suction pump and draining fluid from the sample medium through the filter. The contaminant is collected and left upon the filter ready to be analyzed. Analysis is had by the color comparison or the spot test technique. That is, the filter is impregnated with an analytical chemical material so that the collected chemical contaminant reacts therewith. The reaction causes a color change. Then to establish the presence of a contaminant, the color of the contaminant containing filter is compared with a color chart.
To detect incapacitating agents, I, along with others, have used a fluorescent test. It is based upon the fluorescent complex formed when an agent, such as a glycolate, combines with the indandione detector reagent. The incapacitants which are disseminated as micron-sized solid particles are sampled from the air or from surfaces using glass fiber filters. Sampling is accomplished by inserting a filter into Robertson's apparatus and operating it in the above described fashion. The sample is removed from the apparatus and sprayed with a reagent, the subject of another assignee invention filed in the U.S. Pat. Office on Aug. 7, 1969, entitled Detection of Glycolates and bearing Ser. No. 851,142, which is dispensed from an aerosol type can. The sprayed filter containing the sample is then viewed under ultra-violet light (366 nm) through a Kodak N.9 Wratten photometric filter, manufactured by Eastman Kodak Company of Rochester, New York. This photometric filter isolates all visible radiation below 460 nm. A yellow-orange fluorescence of the exposed portion of the filter constitutes a positive test.
Normally this test for incapacitating agents works well. However, if suspended debris, smokes from burning material, colored signalling smokes, and dusts are present, as would be the case in civil disruption or warfare, they too are collected. While these collected materials do not interfere with the reaction between the agent and reagent, their effect is to mask the fluorescence produced by the agent-reagent complex. This necessitates the use of some technique to separate these interferences from the agent to thereby enable the detection of the fluorescence and/or contaminant.
Separation of these masking materials, after trying diverse methods, is best achieved by thin-layer chromatography. This then requires that the sample must be removed from the filter and redeposited on an adsorbent medium used in thin-layer chromatography. As a result, samples are or have either been lost, contaminated further, or destroyed. Hence, the taking of a second and/or a third sample with tenant uncertain results has been common place. And all too often, after thin-layer chromatography steps detection with or without fluorescence is not reliable.